At the Plum Line, Paul Waldman posts that “Democrats may have lost the battle over voter ID, but the war over voting isn’t over.” Regarding the Supreme Court Decision upholding the Wisconsin voter identification law, Waldman writes:

It may be time for liberals to admit that, barring a significant change in the makeup of the Supreme Court, this just isn’t a battle they’re ever going to win.
That doesn’t mean every challenge to a voter ID law should be dropped. Many of these cases are still important to pursue because the details vary from one state to another. Some laws are more restrictive than others, and it’s important for liberals to press the Court to clearly define what’s permissible and what isn’t. For instance, the Texas law (which is still working its way up to the Court) said that hunting licenses could be used as valid identification, but IDs issued by state universities couldn’t. Everyone understood why the Texas legislature wrote the law that way: hunters are more likely to be Republicans, while students are more likely to be Democrats…

But invalidating voter I.d. laws as a whole will have to wait for a different high court majority. As Waldman reiterates, “no one should fool themselves into thinking that this Court is ever going to rule that the basic requirement to present photo ID at the polls is unconstitutional.”
As for an alternative course of action for Democrats, Waldman suggests:

So where does that leave liberals and Democrats? The best-case scenario in this round of lawsuits is that the Supreme Court upholds the requirements to show ID at the polls (which it has since 2008), but also mandates that states make such requirements less onerous. So liberals have to acknowledge that this is primarily a legislative battle, not a legal one. Last week Oregon passed a law providing that everyone who gets a driver’s license or other ID from the state DMV will automatically be registered to vote unless they opt out. It should be the first of a wave of state laws to make registering and voting as easy and universal as possible.
Conservatives may have won the battle over voter ID. But liberals can still win the war over voting.

In a 2012 article in The Nation, Ari Berman cited another successful strategy:

In May 2011, a poll showed that 80 percent of Minnesotans supported a photo ID law. “Nearly everyone in the state believed a photo ID was the most common-sense solution to the problem of voter fraud,” says Dan McGrath, executive director of Take Action Minnesota, a progressive coalition that led the campaign against the amendment. “We needed to reframe the issue. We decided to never say the word ‘fraud.’ Instead we would only talk about the cost, complications and consequences of the amendment.” According to the coalition, the photo ID law would have disenfranchised eligible voters (including members of the military and seniors) dumped an unfunded mandate on counties and imperiled same-day voter registration. On election day, 52 percent of Minnesotans opposed the amendment.
The amendment’s surprising defeat has ramifications beyond Minnesota. “There’s been an assumption of political will for restricting the right to vote,” says McGrath. “No, there’s not.” The amendment backfired on the GOP. “Voter ID did not drive the conservative base to turn out in the way that Republicans thought it would,” adds McGrath. “Instead, it actually inspired progressive voters, who felt under siege, to fight stronger and turn out in higher numbers.” The minority vote nearly doubled in the state, compared with 2008. Minnesota was a microcosm of the national failure of the GOP’s voter suppression strategy.

In addition, opinion data indicates that Dems have good reason to put more resources into the fight to protect and expand early voting, as Ariel Edwards-Levy reports at HuffPo, citing a HuffPo/YouGov poll:

Sixty percent of Americans say it’s a good thing for states to allow early voting, while just 14 percent say it’s a bad thing. A 39 percent plurality say the current policy on early voting in their state is about right, while another 20 percent would like to see expanded access. Only 11 percent say access in their state should be reduced.

Right now it’s hard to envision a better Supreme Court. That’s going to require a broad Democratic victory in 2016. In the shorter range, however, Dems have plenty of promising alternative strategies for fighting Republican voter suppression.